1. Field of the Invention
The present invention relates to an image forming apparatus transferring a toner image borne on a first belt to a recording medium borne on a second belt.
2. Description of the Related Art
As taught in Japanese Patent Application Laid-Open Publication No. 2009-139752 and in Japanese Patent Application Laid-Open Publication No. 2007-57803, an image forming apparatus in which an image is formed by secondary transferring a toner image primarily transferred from a photosensitive drum to an intermediate transfer belt to a recording medium borne on a secondary transfer belt stretched by a plurality of stretch rollers is widely used.
On the other hand, as taught in Japanese Patent Application Laid-Open Publication No. H04-174454, in an image forming apparatus where the toner image borne on a photosensitive belt is transferred to the recording medium, if the image forming apparatus is left unused for a long period of time, curling may be formed on the photosensitive belt, possibly causing transfer irregularities of the toner image. Therefore, in Japanese Patent Application Laid-Open Publication No. H04-174454, a timer is provided to measure a stop duration time of the photosensitive belt, and when the stop duration time reaches a threshold value, the photosensitive belt is rotated to cancel the curling.
Japanese Patent Application Laid-Open Publication No. 2007-57803 teaches an image forming apparatus having a pair of fur brushes in contact with an intermediate transfer belt and recover transfer residual toner therefrom. Japanese Patent Application Laid-Open Publication No. 2006-259367 teaches an image forming apparatus having a pair of fur brushes arranged to contact a secondary transfer belt and cleaning the belt.
In the image forming apparatus as described above where the toner image borne on the intermediate transfer belt is transferred to the recording medium borne on the transfer belt, transfer irregularities of the toner image may occur when curling occurs to the intermediate transfer belt, similar to the photosensitive belt of Japanese Patent Application Laid-Open Publication No. 4-174454. Further, it has been discovered according to the studies of the present applicant that transfer irregularities may occur not only by the curling of the intermediate transfer belt but also by curling of the transfer belt caused by a stretch roller.
On the other hand, noise may occur when a belt member such as a photosensitive belt is driven, as described in Japanese patent Application Laid-Open Publication No. H04-174454. Therefore, it is needed to stop such belt member as much as possible when images are not formed.